1. Field of the Invention
The present invention is concerned with a teat cup liner, also known as an inflation, for a teat cup which is designed to permit mounting of the liner on a milking claw to provide resistance to cuts and variable amenability to closure of the opening of a corresponding nipple in the milking claw when the liner is in a hanging, non-milking position. By resisting cuts and providing such closure in the non-milking position, the liner reduces the flow of vacuum-drawn air through the channel of the liner and thereby saves energy by reducing the demand on the vacuum pump.
2. Description of the Prior Art
In typical dairy applications, conventional automatic milking machines utilize a plurality of teat cup assemblies connected to a common milk claw. Each of the teat cup assemblies include a hollow outer shell or cup attached to a pulsation line which typically alternates between a vacuum and atmospheric pressure. An inflation or teat cup liner is provided within the teat cup and extends axially along the length thereof. The liner includes a mouthpiece which extends from one end of the teat cup to seal one end of the cup and to receive a teat of an animal to be milked therein, a barrel which surrounds at least a portion of the teat and flexes according to the pulsating pressure, and a short milk tube which extends from and seals the other end of the teat cup for connection to the milking claw. A constant vacuum is drawn through the claw and the liner during milking to extract milk from the animal. Thus, the interior milk and vacuum conveying channel within the liner is maintained at constant sub-atmospheric conditions. A vacuum pump is operable connected to the milking claw by, inter alia, a long milk tube, the vacuum pump being connected to a source of power to create the necessary vacuum for milk extraction.
During milking, the annular region between the cup and the liner is subjected to alternating subatmospheric pressure and a higher, typically atmospheric pressure, while the mouth of the liner is positioned in sealing engagement with the teat. The barrel wall alternately flexes inwardly toward the teat in the teat-receiving region of the barrel and relaxes to a generally straightened position during respective application of elevated (atmospheric) and subatmospheric pressure. This alternating pressure in the annular region effectively causes the barrel wall to massage the teat and thereby promote the extraction of milk.
Once the milk is effectively extracted from one or more of the teats, many automatic milking machines include an automatic take-off feature. The teatcup assembly is removed from the teat of the animal, with a beneficial effect of reducing irritation caused by vacuum and pulsation longer than is necessary to extract the milk. Once the teat cup assembly is removed from the teat, the mouth of the liner is no longer sealed around the teat and air rapidly rushes in. In consequence, a greater demand is placed on the vacuum pump in order to maintain a desired vacuum in the milking system. As multiple claws are commonly connected to a single vacuum pump, other teatcup assemblies may still require vacuum for milking, or even other assemblies attached to the same milking claw which are still connected to another teat of the same animal.
One problem thus encountered during milking is excessive loads placed on the vacuum pump when a teatcup is detached from a teat. As noted in U.S. Pat. No. 5,493,995, the disclosure of which is incorporated herein by reference, one solution provided to control the demands on the vacuum pump is allowing the teatcup assembly to drape over the opening in the short milk nipple of the claw. This practice substantially reduces the flow of air through the passage drawn by the vacuum pump and thereby reduces vacuum demand. However, there are several problems associated with this system. One is that chafing and cuts rapidly occur where the liner engages the short milk nipple. Once a liner is cut, it must be discarded as the leakage of air through the liner impedes proper milking. This increases costs to the dairyman both in terms of material and in labor to inspect and frequently replace liners. Another problem is that not all teat cups are the same, varying in size and weight. As a consequence, making the liner wall of the proper thickness to shut off for one teat cup may not work for a lighter teat cup which has insufficient weight to cause proper bending of the liner. A liner with one wall thickness may be too thick may prevent shut-off, while making the liner wall too thin may cut too rapidly. Furthermore, changes in environmental conditions during the year make the liner more flexible in warmer weather while more rigid in colder weather.
There has thus developed a need for an improved liner which addresses these problems while still reducing energy consumption by the vacuum pump and resisting cutting from the short milk nipple of the claw.
These and other problems have largely been addressed by the variable shut off teat cup liner of the present invention. That is to say, the liner provides a degree of adjustability in regard to the flexibility of the liner in a segment of the short milk tube intended for mounting in engagement with the nipple, while providing improved cut resistance in the segment. The liner is particularly useful with milking claws having short milk nipples with angled edges so that the wall of the liner lays across the nipple opening, with improved cut resistance. A single liner may be used by the dairyman with different claws and different environmental conditions by permitting the dairyman to vary the placement of the liner on the nipple and thus change the relative flexibility in the segment intended for bending over the opening of the nipple of the milking claw.
The liner hereof includes a mouthpiece, a barrel and a short milk tube as is conventional. However, the short milk tube includes a segment including a plurality of grooves to promote bending of the liner in this area when the teat cup liner is detached from the animal""s teat. While the segment is sufficiently stiff to slightly bend but avoid folding by the weight of the liner alone, when the teat cup is attached, it bends sufficiently to drape over the opening of the nipple of the claw when properly mounted. The segment most preferably includes both a plurality of circumscribing grooves and a plurality of longitudinal grooves in the outer surface of the liner wall. The circumscribing grooves are axially spaced at different intervals whereby lugs of different widths are a part of the segment. The resulting larger lugs are preferably located more proximate the mouthpiece of the liner, while the relatively smaller lugs are thereby positioned more proximate the nipple receiving end of the liner. The resulting construction of the segment permits the user to effectively adjust the tendency of the segment to bend according to how far the short milk tube is installed over the nipple. By installing the liner on the nipple of the milk claw to a greater degree, the short milk tube tends to bend at that portion of the segment having the larger lugs and thus is relatively less flexible. If the liner is installed such that a lesser amount of the short milk tube overlies the nipple, then the short milk tube tends to bend in the region of the small lugs where the circumscribing grooves are closer together and thus is more flexible. Thus, the degree of flexibility can be readily adjusted by the dairyman by increasing or decreasing the amount of overlap of the short milk tube over the nipple. Moreover, the longitudinal grooves provide flexibility but tend to cause the lugs on the upper side of the segment to close together when the liner bends in the area of the segment. Thus, the wall thickness of the liner at the lugs having an increased thickness relative to the wall thickness of the liner at the grooves, the lugs of the liner where the greatest bending occurs move toward each other to thereby resist cuts extending through the liner along a possibly sharp edge of the nipple.
These and other advantages of the present invention will be readily apparent to those skilled in the art with reference to the drawing and description which follows.